I. Field of the Invention
This invention relates generally to electrosurgical apparatus, and more particularly to a catheter-based bipolar electrosurgical device which can be passed through an endoscope into the duodenum to the site of the papilla of Vater and which can be deployed to cut the sphincter of Oddi to allow passage of gallstones from the common bile duct in the duodenum.
II. Discussion of the Prior Art
As is set in the "Discussion of the Prior Art" of U.S. Pat. No. 5,035,696 to Rydell, when gallstones form in the gallbladder and achieve a size too large to pass through the cystic duct and the common bile duct into the duodenum, a gallbladder attack may result leading to intense pain and possible surgical removal of the gallbladder itself. Where the site of the blockage is the sphincter of Oddi, a less traumatic procedure referred to as "endoscopic retrograde sphincterotomy" (ERS) may be used to cut the sphincter sufficiently to permit even large size gallstones to pass into the duodenum. In carrying out the ERS procedure, a side-viewing endoscope is passed through the esophagus into the stomach and from there through the pyloric sphincter into the duodenum. Using a fiber optic bundle, the distal end of the endoscope is made to approach the papilla of Vater and, when so positioned, a cannula is passed through the endoscope and through the sphincter of Oddi into the common bile duct. At this point, a contrast fluid may be injected so that any gallstones can be viewed fluoroscopically and their size evaluated. If a stone is deemed to be too large to pass through the sphincter of Oddi even when enlarged, the sphincterotomy procedure is terminated and the patient at that point becomes an abdominal surgery candidate. However, if the size of the gallstones are sufficiently small, an electrosurgical instrument referred to as a sphincterotomy or papillotome is made to pass through a side port in the endoscope and through the sphincter of Oddi. At this point, the instrument is used to cut the sphincter of Oddi to effectively allow it to expand and pass gallstones of a size too large to pass through that sphincter normally.
Electrosurgical sphincterotomies of the prior art have been monopolar in nature. In particular, it would typically comprise an elongated tube having a proximal end, a distal end and a lumen extending between the two ends. A small aperture is formed a short distance proximal of the distal end and a conductive wire is routed through the lumen of the tube, out the aperture and then anchored proximate the distal tip of the tube. This wire would be electrically coupled to an electrosurgical generator whose other terminal connects to an indifferent electrode called a patient plate placed in electrical contact with the patient's buttocks. By applying a tension force to the proximal end of the aforementioned wire following its placement through the sphincter of Oddi, the tip portion of the sphincterotomy becomes bowed and when the voltage is applied between the wire and the patient plate, a current flows from the wire through contacting tissue and from there through a path of least resistance to the patient plate. This type of monopolar sphincterotomy is more particularly described in Demling et al. German Offenlegungsschrift 24 26 781.
The use of a monopolar sphincterotomy has led to a number of problems, chiefly due to the unpredictable nature of the current return path through the body to the patient plate. Where conductive fluids have been introduced into the common bile duct at the outset to assess stone sizes, that fluid also finds its way into the pancreatic duct which is directly adjacent the sphincter of Oddi. Recognizing that the contrast fluid is a highly conductive liquid, one path of least resistance from the monopolar cutting wire to the patient plate is through pancreatic tissue. This current flow has been found to raise the temperature of the pancreas to the point where cells become inflamed, leading to a serious condition called "pancreatitis". It is also found the depth of tissue destruction resulting from a monopolar electrosurgical sphincterotomy may be excessive and in some instances, this has led to a perforation of the bowel. In this event, the patient must undergo abdominal surgery to correct that condition.
In that the site of the sphincter of Oddi is highly vascularized, considerable bleeding takes place during a ERS procedure, especially where a monopolar electrosurgical sphincterotomy is employed.